This invention relates to an enclosure for electrical apparatus providing, in an overall light and rigid structure, total isolation of the electrical apparatus from ambient conditions while preserving excellent heat transfer proficiency.
When electrical apparatus must be placed inside an enclosure, it is necessary to prevent temperature build-up due to heat accumulation in, or around, the electrical parts. Usually external air is blown inside and through the enclosure in order to evacuate the accumulated heat. However, it is not desirable to do so when the equipment is operated in a dirty, hostile atmosphere, since particles introduced into the enclosure could cause electrical failure.
It is known to cool electrical equipment with air-to-air liquid-to-air heat exchangers in direct contact with the critical electrical parts (for instance electrodes) or rather with a heat sink, in order to remove the heat toward a heat dissipator.
It is also known to remove localized hot spots of an electrical apparatus with a heat pipe, e.g. a sealed off device containing a liquid which is vaporized on a side exposed to the heat sink, and condensed on the side exposed to the heat dissipator. Vaporization chambers are known which contain a fluid which takes up heat by vaporization against a hot wall, the vapor being spread onto a cool wall where it is being condensed and returned by gravity for reuse along the hot wall thereof. The essential distinctions between a heat pipe and a vaporization chamber are:
A. A heat pipe is used for localized heat transfer. It returns the condensate to the reservoir via capillary action in a wick, thus, it can operate under conditions of zero gravity. Physically, they are tubular in shape with a large length to diameter ratio. PA1 B. A vapor chamber uses only gravity to return condensate to the reservoir. Its function is to transfer heat in a gross or macro sense of an apparatus rather than a localized hot spot.